Corneal Surgery apparatus

ABSTRACT

An ophthalmic surgery apparatus comprising a system for observing an anterior portion of an eye, and an optical system for irradiating a laser beam for treatment to the eye, the apparatus is a corneal surgery apparatus irradiating the laser beam to a cornea and ablating a surface thereof, the apparatus comprising a moving device for moving the optical system relatively against the eye, an illuminating device for illuminating a large area of the anterior portion of the eye, a photoelectric transducing device having a two-dimensional light sensing plane, for sensing distribution of light volume of the anterior portion of the eye, a pupil position sensing device for sensing the position of a pupil, a control device for controlling the moving device based on sensed results, a tracking signal generating device for generating a signal to track movement of the eye, whereby the moving device is controlled by the control device so as to track movement of the eye by inputting a signal generated by the tracking signal generating device, and a device for prohibiting irradiation of the laser beam in the case that the position of the pupil misses the predetermined limits.

This is a Division of application Ser. No. 08/979,846 filed Nov. 26,1997, now U.S. Pat. No. 6,159,202, which in turn is aContinuation-In-Part of application Ser. No. 08/714,809, filed Sep. 17,1996, now abandoned. The entire disclosure of the prior applications arehereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ophthalmic surgery apparatus whichtreats by irradiating a laser beam to an eye of a patient, and moreparticularly to a mechanism for delivering the laser beam to a desiredposition of the eye and for tracking movement of the eye.

2. Description of the Related Art

As an ophthalmic surgery apparatus which treats by irradiating a laserbeam to an eye of a patient, for example, a corneal surgery apparatuswhich uses an excimer laser beam is known. This apparatus ablates asurface of a cornea by irradiating the excimer laser beam so as toremove a diseased portion of the cornea and corrects an ametropia bychanging a curvature of the cornea.

In the case that this apparatus is used, an operator makes the patientfix a fixation target with the eye, then aligns an irradiating opticalsystem with the eye so as to be desired condition with observing analignment target. The alignment is completed, then the operator makesthis apparatus irradiate the laser beam so as to ablate determinedamount of a desired area of the eye.

Though the patient is made to fix the fixation target with the eye, ifan eyeball of the eye happens to move during the alignment or the laserbeam irradiation and the movement is confirmed by the operator, then theoperator must do the alignment over again once more from beginning, orthe operator must discontinue the laser beam irradiation and do thealignment over again.

As described above, doing the alignment over again is a burden to boththe patient and the operator because of taking much a long time for itsoperation or the like. Furthermore, in the case that the eyeball movesoften, the burden is much more.

And if the operator does not notice the movement of the eyeball andcontinues the laser beam irradiation, then the cornea is not ablated soas to be an expected shape, therefore a refractive power of the eyeafter the operation is influenced thereby.

Furthermore, if the operator is not accustomed to operating theapparatus, then the alignment itself takes much time.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstancesand has an object to overcome the above problems, and to provide anophthalmic surgery apparatus, which may make it easy to align a laserbeam irradiating optical system with an eye of a patient withoutburdening both a patient and an operator.

Additional objects and advantages of the invention will be set forth inpart in the description which follows and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and attained bymeans of the instrumentalities and combinations particularly pointed outin the appended claims.

To achieve the objects and in accordance with the purpose of theinvention, as embodied and broadly described herein, an ophthalmicsurgery apparatus comprising an observation optical system for observingan anterior portion of an eye of a patient, and a laser beam irradiatingoptical system for irradiating a laser beam for treatment to the eye,the ophthalmic surgery apparatus is a corneal surgery apparatusirradiating the laser beam to a cornea of the eye and ablating a surfaceof the cornea, the apparatus comprises a moving means for moving thelaser beam irradiating optical system relatively against the eye, anilluminating means for illuminating a large area of the anterior portionof the eye, a photoelectric transducing means having a two-dimensionallight sensing plane, for sensing distribution of light volume of theanterior portion of the eye illuminated by the illuminating means, apupil position sensing means for sensing the position of a pupil byprocessing the signal transmitted by the photoelectric transducingmeans, a control means for controlling the moving means based on resultssensed by the pupil position sensing means, a tracking signal generatingmeans for generating a signal to track movement of the eye, whereby themoving means is controlled by the control means so as to track movementof the eye by inputting a signal generated by the tracking signalgenerating means, and an irradiation prohibiting means for prohibitingirradiation of the laser beam in the case that the position of the pupilmisses the predetermined limits.

In another aspect of the present invention, an ophthalmic surgeryapparatus comprising an observation optical system for observing ananterior portion of an eye of a patient, and a laser beam irradiatingoptical system for irradiating a laser beam for treatment to the eye,the ophthalmic surgery apparatus is a corneal surgery apparatusirradiating the laser beam to a cornea of the eye and ablating a surfaceof the cornea, the apparatus comprises a moving means for moving thelaser beam irradiating optical system relatively against the eye, anilluminating means for illuminating a large area of the anterior portionof the eye, a photoelectric transducing means having a two-dimensionallight sensing plane, for sensing distribution of light volume of theanterior portion of the eye illuminated by the illuminating means, apupil position sensing means for dividing a sensing area of thephotoelectric transducing means into the predetermined number, thensensing the position of a pupil based on analysis and comparison forlight-and-shade information of the divided respective areas, a pupilposition sensing means divides the two-dimensional sensing plane into atleast more than four members, then senses the position of a pupil basedon bias of the light-and-shade which is obtained every divided area, anda control means for controlling the moving means based on results sensedby the pupil position sensing means.

In another aspect of the present invention, an ophthalmic surgeryapparatus comprising an observation optical system for observing ananterior portion of an eye of a patient, and a laser beam irradiatingoptical system for irradiating a laser beam for treatment to the eye,the ophthalmic surgery apparatus is a corneal surgery apparatusirradiating the laser beam to a cornea of the eye and ablating a surfaceof the cornea, the apparatus comprises a moving means for moving thelaser beam irradiating optical system relatively against the eye, anilluminating means for illuminating a large area of the anterior portionof the eye, a photoelectric transducing means having a two-dimensionallight sensing plane, for sensing distribution of light volume of theanterior portion of the eye illuminated by the illuminating means, apupil position sensing means for dividing a sensing area of thephotoelectric transducing means into the predetermined number, thensensing the position of a pupil based on analysis and comparison forlight-and-shade information of the divided respective areas, a pupilposition sensing means including a light-and-shade sensing means fordividing the two-dimensional light sensing plane into some number whichhave areas not adjacent each other, then obtaining the light-and-shadeinformation every the divided area, a judging means for judging whetherthere is difference of the predetermined light-and-shade degree in thelight-and-shade information of areas not adjacent each other and a pupilposition specifying means for specifying that the pupil exists in darkside area in the case that the judging means judges that there is thedifference of the predetermined light-and-shade degree and a controlmeans for controlling the moving means based on results sensed by thepupil position sensing means.

Further, in another aspect of the present invention, an ophthalmicsurgery apparatus further comprises a threshold level determining meansfor determining a threshold level for use in specifying a pupil area,and wherein the pupil position sensing means senses the position of thepupil based on the threshold level determined by the threshold leveldetermining means and the signal of distribution of light volumetransmitted by the photoelectric transducing means.

According to the present invention, it is capable of preventing anirradiating area from deviating, and is capable of treating an eye of apatient appropriately, because the apparatus can track the eye even ifan eyeball of the eye moves during the laser beam irradiation. Also, astable tracking can be realized with reducing an effect caused by anoise light.

Furthermore, since the performance for operating is improved, so burdenis allowed to be decreased for both the patient and the operator.Furthermore, the trouble of the alignment is allowed to be decreased,therefore the alignment adjustment can be performed easily.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to theaccompanying drawings in which:

FIG. 1 is an external view showing a whole schematic configuration of anapparatus for a corneal surgery according to the preferred embodiment ofthe present invention;

FIG. 2A is a view showing optical elements arrangement of inside of anarm part of an apparatus;

FIG. 2B is a view showing movement mechanism of an arm part;

FIG. 3 is a schematic view showing an optical system of an apparatus ofthe preferred embodiment of the present invention;

FIG. 4 is a view showing an image of an anterior portion of an eye of apatient photographed by a CCD camera;

FIG. 5 is a view showing distribution of light volume on line A-A′ shownin FIG. 4;

FIG. 6 is a block diagram for a control system of an important part ofan apparatus according to the preferred embodiment of the presentinvention;

FIG. 7 is a view showing an example for the image divided into 16 areaswith the center at an optical axis O relative to a two-dimensional imagesent by a CCD camera;

FIG. 8 is a flowchart for illustrating procedure for an automaticalignment which moves an arm part to X,Y-directions based onlight-and-shade information;

FIG. 9 is a view showing an image of an anterior portion of an eye of apatient photographed by a CCD camera;

FIG. 10 is a view showing distribution of light volume on line A—A shownin FIG. 9; and

FIG. 11 is a flowchart for illustrating operation of an apparatus of thepreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One preferred embodiment according to the present invention will be nowdescribed with reference to the accompanying drawings.

[General Construction]

FIG. 1 is an external view showing a schematic construction of anapparatus for a corneal surgery by using an excimer laser beam.Reference numeral 1 indicates a primary body of a surgery apparatus, inwhich an excimer laser beam source and the like are contained. The laserbeam irradiated from the excimer laser beam source is reflected bymirrors inside the body 1, then is delivered to an arm part 2. An edgepart of the arm part 2 is provided with an observation optical part 5including a binocular microscope 3 for observing a patient's eye 15, anillumination part 4, a laser beam irradiating orifice not shown, aneyeball position detecting optical system mentioned-below or the like.The illumination part 4 is provided with a visible-rays illuminationlight source which emits a light within a range of visible-rays, usedfor that an operator observes the patient's eye, and an IR-raysillumination light source 20 which emits a light within a range ofinfrared-rays for use in detecting position of an eyeballmentioned-below.

The laser beam is delivered to the patient's eye by some opticalelements such as mirror disposed inside the arm part 2 and theobservation optical part 5 (see FIG. 2A). As shown in FIG. 2B, the armpart 2 moves in X-direction (lateral direction to the operator) undercontrol of a X-direction arm driving device 31 a and moves inY-direction (forward and backward directions to the operator) undercontrol of a Y-direction arm driving device 31 b. Also, the observationoptical part 5 moves in Z-direction (direction of a laser beamirradiating optical axis) under control of a Z-direction arm drivingdevice 32. Respective arm driving devices 31 a, 31 b and 32 consists ofa motor, a sliding mechanism or the like.

Reference numeral 6 indicates a controller, which includes a joystick 7for giving a signal for driving the arm part 2 in X,Y-directions, andseveral kinds of operating switches such as a focus-adjusting switch 60for performing an alignment of Z-direction, an automatic alignmentswitch 61 for desiring a change between ON and OFF of an automaticalignment, a Ready switch 62 for changing its state from stand-by tosuch state as being capable of irradiating the laser beam. Referencenumeral 8 indicates a foot switch for sending a laser emission signal,and 9 indicates a computer for inputting some kinds of necessary data ofoperating condition, for calculating, displaying, storing the laserirradiating data, or the like. The computer 9 consists of a primary body90, a monitor 91, a keyboard 92, a mouse 93 or the like. Referencenumeral 10 is a bed to make the patient lie down thereon.

[Constructions of Respective Components]

(Optical System)

FIG. 3 is a schematic view showing an optical system of the apparatus ofthe preferred embodiment.

(A) Laser Beam Irradiating Optical System

Reference numeral 11 indicates the laser beam source for irradiating theexcimer laser beam of 193 nm wave length. 25 indicates a plane mirrorcapable of reflecting the laser beam, which is emitted by the laser beamsource 11 to horizontal direction, to upper direction of 90 degrees. 26indicates a plane mirror capable of moving to vertical direction(denoted by an arrow), which causes the laser beam to be polarized tohorizontal direction once more. 27 indicates an image rotator whichcauses the laser beam to rotate around an optical axis L (the laser beamirradiating optical axis). 12 indicates an aperture for limiting anirradiating area of the laser beam, of which the aperture diameter iscan be changed by an aperture driving device not shown. 13 is aprojection lens for projecting the aperture 12 onto a cornea Ec of thepatient's eye 15. The aperture 12 is located on a conjugate positionwith the cornea Ec via the projection lens 13, and the area limited bythe aperture 12 is projected onto the cornea, thereby the area ofkeratectomy (ablation) is limited. The laser beam having a rectangularcross section irradiated from the laser beam source 11 moves to thepredetermined direction based on parallel movement of the mirror 26, andcovers whole area of the aperture 12. Ablation performed by controllingmovement of the mirror 26 and an opening-degree of the aperture 12 aredisclosed in Japanese Patent Laid-Open No. HEI4-242644(corresponding toU.S. Pat. No. 5,507,799) to be referred.

Reference numeral 14 indicates a dichroic mirror having suchcharacteristics that reflects the excimer laser beam and transmits thevisible-rays and the infrared-rays, enabling the optical axis of thelaser beam irradiating optical system to coincide with an optical axisof an objective lens of an observation optical system mentioned-below.In the case of coinciding with a guide light on the light source side,the dichroic mirror 14 is made to have characteristics reflecting a partof the guide light.

(B) Observation Optical System

Reference numeral 17 indicates the objective lens, 18 indicates adichroic mirror having characteristics of transmitting the visible-raysand of reflecting the infrared-rays. An image of an anterior portion ofthe patient's eye 15, which is illuminated by the visible illuminationlight from the visible-rays illumination light source not shown, istransmitted to the microscope 3 via the dichroic mirror 14, theobjective lens 17 and the dichroic mirror 18. The operator observes thepatient's eye 15 by using the microscope 3. A reticle plate not shown isinserted into the observation optical system and the reticle plate canbe the standard for the alignment in X,Y-directions of the patient's eye15.

Also, an target projecting system composed of two slits (see JapanesePatent Laid-Open No. HEI6-47001 corresponding to U.S. Pat. No.5,562,656) is disposed in the observation optical system in order toperform the alignment in Z-axis direction. 16 indicates a fixation lampplaced on the optical axis of the objective lens 17.

(C) Eyeball Position Detecting Optical System

Reference numeral 20 indicates the IR-rays illumination light sourcesuch as LED which emits the light within the range of near infrared-raysor the like, and 4 members of the IR-rays illumination light sources 20are disposed at intervals of 90 degrees each other around the opticalaxis. 22 is a reflecting mirror, 23 is an IR-rays transmitting filter,and 24 is a CCD camera having sensitivity within the range of nearinfrared-rays. A photo-imaging plane of the CCD camera 24 is arranged soas to be approximately conjugate with a position close to a pupil of thepatient's eye 15 with respect to the objective lens 17.

The image of the anterior portion of the patient's eye 15 illuminated bythe IR-rays illumination light source 20 is formed on the photo-imagingplane of the CCD camera 24 via the dichroic mirror 14, the objectivelens 17, the dichroic mirror 18, the reflecting mirror 22 and theIR-rays transmitting filter 23. At this moment, the IR-rays transmittingfilter 23 cuts slightly the visible-rays reflected by the dichroicmirror 18. A signal of the image photographed by the CCD camera 24 isinputted to a control device 30 mentioned-below.

The CCD camera 24 detects the eyeball position as following. FIG. 4shows the image of the anterior portion of the patient's eye 15photographed by the CCD camera 24, and FIG. 5 shows a view ofdistribution of light volume on line A-A′ (FIG. 4) based on the imagesignal from the CCD camera 24. As shown in figures, the respective lightvolumes are different by which a pupil, an iris, a sclera, thereforeaccording to this information, pupil edge coordinates in lateraldirection can be detected, furthermore, in accordance with detection ofthe pupil edge, the center position, so called, a pupil centercoordinate in lateral direction is can be obtained. In the same way asis described, the pupil center coordinate in longitudinal direction canbe obtained by using information of distribution of light volume onlongitudinal line B-B′. Therefore, in accordance with both of them, thepupil position relative to the optical axis of the detecting opticalsystem (so called the optical axis of the laser beam irradiating opticalsystem), which is regulated so as to be the predetermined positionalrelationships on the photo-imaging elements of the CCD camera 24, isobtained. Still, the lateral and longitudinal detecting lines arepreferably to be averaged in response to the information concerningdistribution of light volume of plural lines with the center at themiddle of the photo-imaging elements of the CCD camera 24.

Furthermore, if the processing time permits, the position of the centerof gravity may be obtained based on the whole pupil area.

In addition, the light by corneal reflection of the IR-rays illuminationlight source 20 is also transmitted to the CCD camera 24, however if theIR-rays illumination light source 20 is arranged so that a cornealreflex may not interrupt the detecting lines (lateral and longitudinal),then the light by corneal reflection is prohibited from becoming noiselight at the time when positional coordinates are to be detected. Thatis, the line linked by two opposite light sources is made to slant to 45degrees relative to the detecting lines (lateral and longitudinal), andis made so that the image of the light source may be formed at peripheryside of the cornea. Besides, the preferred embodiment does notrestricted by such composition of above-mentioned arrangement, thereforevarious changes and modifications may be made as far as the pupil edge(or the iris) can be detected.

(D) Control System

FIG. 6 shows a block diagram for a control system of an important partof the apparatus according to the preferred embodiment of the presentinvention. Reference numeral 30 denotes the control device forcontrolling whole of the apparatus. The image signal outputted by theCCD camera 24 is converted to binary form by a signal-sensing processingcircuit 34, then is given the predetermined process, and then isinputted into the control device 30. The control device 30 detects thepupil position based on signals of light volume every respective allpixel (or the predetermined pixel), then drives and controls respectivearm driving devices 31 a, 31 b and 32.

Next, method for detecting the pupil position will be describedhereinafter. FIG. 9 shows the image of the anterior portion of the eyephotographed by the CCD camera 24, FIG. 10 shows distribution of lightvolume on a scanning line A—A (the line A—A is shown in FIG. 9). Theimage obtained by the CCD camera 24 is that distribution of light volumedepends on the pupil or the iris (except the pupil), therefore,respective levels of light volume for both the pupil and the iris aredetermined on the basis of the distribution information of light volume.

Determination of levels of light volume for both the pupil and the irisis made as follows. On the distribution information of light volume,volume of reflected light of the pupil is extremely little, thereforethe section, of which the level of light volume is the lowest, isextracted among that of all pixel. The pupil is allowed to be consideredas being within a range from the lowest level of light volume to acertain level of light volume, therefore the data of the pixel positionand the data of light volume being within the predetermined range Δl areobtained with defining the lowest level of light volume as standard. Atthis time, the data of the pixel position, not adjacent to each other,is preferably excluded. Then obtained data of light volume are averaged,thereby a light volume level I1 of the pupil is determined.

Next, on the basis of above-mentioned data of the pixel position of thepupil, respective data of light volume every pixel positions (or everypredetermined intervals) is obtained, where are separated thepredetermined range d2 (a range, which is certainly within the iris, maybe desired in advance, or may be calculated based on distribution changeof light volume) toward both sides from respective positions beingseparated the predetermined pixel interval d1 (in order to eliminateeffect caused by change of light volume of the pupil and the iris) frompixel positions of both edges defined as pupil every scanning line. Thenobtained data of light volume are averaged, thereby a light volume levelI2 of the iris is specified.

Respective levels of light volume of the pupil and the iris arespecified, then threshold level of light volume, which is used fordetermining a pupil area therebetween, is determined. Difference betweenthe level of light volume of the pupil and that of the iris is large,therefore, a threshold level I3 is determined in the middle therebetweenin the preferred embodiment. The data of the pixel position having lowerlight volume than the threshold level I3 is detected from whole of ascreen image, whereby the pupil area 50 is determined (see FIG. 9).After that, xy-coordinates are substituted for distribution of thepixel, then the position of the center of gravity of the area 50 isobtained on coordinates (at this time, related to the axis ofcoordinates, the process will be easier by defining the center of thescreen as (x, y)=(0, 0), and defining the position (0, 0) as the laserbeam irradiating optical axis), thereby the obtained position of thecenter of gravity is defined as the center of the pupil. A relativeposition of the pupil can be sensed by comparing the optical axis of thedetecting optical system which is adjusted so as to be the predeterminedpositional relationships on the photo-imaging elements of the CCD camera24 (that is the optical axis of the laser beam irradiating opticalsystem), and the position of the pupil center.

Besides, above-mentioned threshold level I3 (or the level I1 of lightvolume of the pupil, the level I2 of light volume of the iris) may bedetermined in advance based on light volume of standard pupil and thatof standard iris, simply. Also, this is allowed to be changed anddesired by the operator depending on the surgery circumstance.

Referring to above-mentioned sensing of the pupil position, even if thenoise light 51, caused by an illumination light or the like, is thrownto the pupil area or an area close to edge of the pupil, then positionof the pupil center can be detected stably without being influenced byit so much. Furthermore, the position of the pupil center can bedetected precisely without being related to shape of the pupil edge.

The operation of the apparatus, having such architecture as describedabove, will be described below. The ophthalmic surgery apparatus isconnected to a power source and the system is made to run, a menu frameis displayed on the monitor 91 of the computer 9. The ways of thecorneal surgery by using the excimer laser beam are PRK (photorefractivekeratectomy) operating mode and PTK (phototherapeutic keratectomy)operating mode, in this case, the operator selects the PRK operatingmode from the menu frame. The operator inputs several kinds of data suchas a refractive power value of the patient's eye 15 and operatingconditions or the like, which are inspected beforehand, with thekeyboard 92 of the computer 9. The primary body 90 of the computer 9calculates the ablating amount of the cornea and the like, based on theinputted data. The calculated operating data are inputted to the controldevice 30 by operating the keyboard 92.

After the input preparations is completed, the operator makes thepatient lie down on the bed 10, then places the observation opticalsystem 5 provided the laser beam irradiating orifice above the patient'seye 15. The operator turns on respective light sources, and causes thepatient's eye 15 to gaze at the fixation lamp 16.

The operator observes the image of the anterior portion of the patient'seye 15 illuminated by the visible light illuminating light source withthe microscope 3, and performs the alignment in X,Y-directions, so thata reticle not shown and the pupil may be the predeterminedrelationships, by operating the joystick 7, and performs the alignmentin Z-direction by operating the focus-adjusting switch 60. The controldevice 30 causes respective arm driving devices 31 a, 31 b and 32 to gointo run based on signals generated by the joystick 7 and thefocus-adjusting switch 60, thereby moves the arm part 2 toX,Y-directions and moves the observing optical part 5 to Z-direction.

At the time of this alignment, condition for operating is such that theapparatus can select the automatic alignment, which performs thealignment in X,Y-directions based on the detection of the pupil centermade by the eyeball position detecting optical system by controlling aworking of the arm driving devices 31 a and 31 b. Once the automaticalignment switch 61 is turned on, the automatic alignment goes into run(see a flowchart shown in FIG. 11). Once the patient's eye 15 enters anarea where position of the center of gravity of the pupil area 50 can bedetected by the eyeball position detecting optical system (it is can bejudged whether the pupil area 50 exists on the center coordinatescorresponding to the center of optical axis), then the control device 30causes the arm part 2 to move to X,Y-directions so that the pupil centerobtained as mentioned above may coincide with the laser beam irradiatingoptical axis.

For example, in the case that coordinates of the pupil center is (x,y)=(40, 0), if the arm part 2 is made to be moved forty-scales ofcoordinates along X-direction, then the pupil center coincides with thelaser beam irradiating optical axis (in the case that the screen centeris coincided with the laser beam irradiating optical axis with definingcoordinates of the screen center as (x, y)=(0, 0) ).

In the case of performing the laser irradiation under the condition thatthe laser beam irradiating optical axis coincides with the pupil centeras they are, after confirming that the alignment is completed, the Readyswitch 62 on the controller 6 is pressed. The control device 30 storesthe predetermined position on the photo-imaging elements of the CCDcamera 24 (position of the optical axis of the laser beam irradiatingoptical system) as a standard position, then causes the eyeball trackingmechanism, which moves the arm part 2 so that the standard position maycoincide with the pupil center (so that it may enter into thepermissible area), to go into run. The position of the pupil centerobtained by processing signals from the CCD camera 24 is compared withthe standard position at all times, if the patient's eye 15 movesexceeding the predetermined permissible area, then the control device 30causes the X,Y-directions arm driving devices 31 a and 31 b to workbased on a compared information, thereby the arm part 2 is made to moveto X,Y-directions so that the position of the pupil center may enter thepermissible area of the standard position. Also, once the eyeballtracking mechanism works in response to a signal inputted by the Readyswitch 62, then after confirming that the eyeball is within a rangecapable of being tracked, a safety-shutter device 35 is released inorder to allow performing the laser irradiation by using the foot switch8.

Then, once the operator steps on the foot switch 8, the control device30 causes to emit the laser beam. The patient's eye 15 is irradiatedwith the excimer laser beam via the laser beam irradiating opticalsystem, and the determined amount of the desired area of the cornea Ecis ablated.

At this time, the pupil center, which is deviated extremely, does notdetected even if noise light exists at the pupil area of the patient'seye 15 or at the area close to the pupil edge owing to the eyeballposition detecting optical system of the apparatus. Thereby, a stableablation can be achieved with preventing the eyeball tracking mechanismfrom making an error. Still, in the case that the patient's eye 15 movesexceeding a moving range in X,Y-directions of the arm part 2 during thelaser irradiation, the safety-shutter device 35 is made to work in orderto intercept the laser irradiation.

In the case that the laser irradiation is performed by aligning thelaser beam irradiation optical axis to be an optional position relativeto the cornea of the patient's eye 15, the alignment is performed byusing the joystick 7 with respect to an target position. After thealignment is completed, once the Ready switch 62 is pressed, then thecontrol device 30 stores coordinates of the pupil center on thephoto-imaging elements of the CCD camera 24 as the standard position (inthe case of working the automatic alignment, once operating signal ofthe joystick 7 is inputted, then the coordinates position of the pupilcenter obtained by offsetting its portion, is stored as the standardposition).

In the case that the eyeball moves, the eyeball tracking mechanism,which moves the arm part 2 so that the pupil center may coincide withthe stored standard position (so that it may comes into the permissiblearea), is made to work.

In the preferred embodiment as described above, the detection of theeyeball position calculates the pupil edge based on the information ofdistribution of light volume of the anterior portion of the eye, andthereby the pupil center is obtained on the basis of the pupil edge,however, since the reflecting light volume from the pupil is extremelylittle among the reflecting light volume of the pupil, that of the iris,that of the sclera and that of a scillosis, therefore it may be alsoallowed that the pupil position (deviating direction from the opticalaxis) is detected according to light-and-shade degree of distribution oflight volume on the photo-imaging element of the CCD camera 24. Infollowing, an alignment performed by this detection will be described.

At first, on detecting light-and-shade information of the reflectinglight from the anterior portion of the eye, as shown in FIG. 7, theimage with the center at the optical axis O is divided into 16 areas (S1to S16) of 4×4 relative to a two-dimensional image from the CCD camera24. The positions of the pixel are previously determined, relative tothe pixel of respective areas (125 pixel×125 pixel), so that thepredetermined number of the pixel (for example, 64 articles), which aredefined as objects to be detected for light-and-shade, may equallydistributed in the area (all the pixel can be the objects to bedetected, however if the required number for detecting are taken as theobjects, the processing speed can be faster). Image signals from the CCDcamera 24 are digitized by the signal-sensing processing circuit 34,then are given by the predetermined process, and then inputted to thecontrol device 30. Based on the inputted signals, the control device 30obtains the light-and-shade degree in response to the pixel which arepreviously determined every respective area. Since the light-and-shadedegree every one pixel is converted to binary form, therefore, forexample, it can be obtained as the numerical value of thelight-and-shade degree of 256 grades from 0 to 255(0 side is thedarkest, 255 side is the brightest).

Then, the operation of the automatic alignment, which detects the pupilbased on obtained light-and-shade value, and drives and controls the armpart 2 in X, Y-directions, will be described hereinafter with referringto a flowchart shown in FIG. 8.

If the automatic alignment switch 61 is turned on, the automaticalignment goes into run according to the detection of the pupil based onthe light-and-shade value. The control device 30 obtains information ofthe light-and-shade value on the pixel which is previously determinedevery respective areas, then extracts the light-and-shade information ofthe predetermined grades (for example, 20 grades) based on the lowest(the darkest) grade of the light-and-shade value as the standard amongthem, and counts the number of the pixel within the predetermined rangeof light-and-shade value in respective areas. Then, it is judged thatwhether the number of the pixel, which are counted in respective areas,satisfies the predetermined number (for example, 20 articles) or more,or not. In the case that it satisfies the predetermined number, it isjudged that the pupil (or the iris around the pupil) exists in the area.In the case that the number of the pixel is little, it is judged thatthe pupil is not detected, since only a part of the pupil enters intothe area, or the section, of which the light-and-shade value is low suchas eyelashes, is overlapped on.

In the case that there are the plural areas which satisfy thepredetermined number (20 articles) and there are ones which are notadjacent each other among the plural areas, it is judged whether thereare differences of the predetermined number (10 articles) or not bycomparing the number of counted pixel of the area having largest numberwith the number of counted pixel of the area not adjacent to the areahaving largest number. Because, even if there are eyelashes or the likedetached from the pupil, in the case that there are some differencesbetween the number of counted pixel, it is taken that the pupil existsin the area which has larger number, and thereby it is distinguishedfrom eyelashes or the like. In the case that there are not thedifferences of the predetermined number (10 articles), it is taken thatthe pupil is not detected. In the case that there are the differences ofthe predetermined number, it is specified that the pupil exists in thearea of which the number of counted pixel are the largest, after that,it is judged that whether the number of counted pixel of the 4 membersof areas S6, S7, S10, S11, with the center at the optical axis O, areequal (equal within the predetermined range) or not, if there aredifferences, according to the position of the area of which the pupilexists, the X,Y-directions arm driving devices 31 a and 31 b are drivenand controlled toward the direction to which the differences aredissolved. Once the differences of the number of counted pixel of the 4members of areas S6, S7, S10, S11 are dissolved completely, drivingtoward X,Y-directions is made to stop (is not made to drive), therebythe automatic alignment is completed.

Still, on detecting the pupil based on the above-mentionedlight-and-shade information, the division of the area in response to thetwo-dimensional image from the CCD camera 24, it may also be capable ofdividing into 4 areas with the center at the optical axis O, simply.

Additionally, concerning control for movement of the arm part 2, itbecomes more convenience to use together with movement control based onthe pupil center calculated by using the above-mentioned pupil edge. Thealignment in large range is performed according to the detection of thepupil based on the light-and-shade information, and when the pupil edgedetection is made to be possible, the alignment is performed in detailaccording to the position of the pupil center based on the detection ofthe pupil edge. Thereby, if it can be capable of observing the pupil ofthe patient's eye in the observation optical system, both the alignmentin large range and the more accurate alignment are realized.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Forinstance, this invention can be enforced without related to theconstruction of the optical system of the laser beam irradiating opticalsystem such as correction of refractive error or the like, and in thecase of the eyeball tracking which based on the position of the opticalaxis, decided by the operator, of the laser beam irradiating opticalsystem, the alignment operation is also easier by deciding the positionin previous inspection and inputting the difference between the positionand the pupil center.

The forgoing description of the preferred embodiment of the inventionhas been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the variations to the preciseform disclosed, and modifications and variations are possible in lightof the above teachings or may be acquired from practice of theinvention. The embodiment chosen and described in order to explain theprinciples of the invention and its practical application to enable oneskilled in the art to utilize the invention in various embodiments andwith various modifications as are suited to the particular usecontemplated.

It is intended that the scope of the invention be defined by the claimsappended hereto, and their equivalents.

What is claimed is:
 1. A corneal surgery apparatus for ablating a corneaof an area used for sight of a patient's eye, comprising: an observationoptical system for observing an anterior portion of the eye; a laserbeam irradiating optical system for irradiating a laser beam whichcauses a cornea of the eye ablation; illuminating means for illuminatinga relatively large area including an iris of the eye; a two-dimensionalphotographing element for photographing a pupil and the iris of the eyeilluminated by said illuminating means; pupil center detecting means fordetecting a pupil center based on pupil information obtained byprocessing a signal transmitted by said photographing element; storagemeans for storing a predetermined position of said photographingelement; and moving means for moving said irradiating position, byobtaining deviation between the position of the pupil center detected bysaid pupil center detecting means and the predetermined position of saidphotographing element stored by said storage means, so that the detectedpupil center position may be placed within a predetermined permissiblerange of the stored position of said photographing element.
 2. A cornealsurgery apparatus according to claim 1, wherein the pupil centerdetecting means comprises arithmetic means for calculating a position ofan outer circumference of the pupil based on said pupil information andcalculating the pupil center based on the position of the outercircumference of the pupil.
 3. A corneal surgery apparatus according toclaim 1, wherein said laser beam irradiating optical system includes agenerating light source of an excimer laser beam, whereby the cornea ofthe eye is ablated by said excimer laser beam generated by said lightsource.
 4. A corneal surgery apparatus according to claim 1, furthercomprising: drive signal generating means for generating a signal fordriving said moving means so that the position of the pupil centerdetected by said pupil center detecting means may be placed within thepredetermined permissible range of the stored position of saidphotographing element, at the time when the position of the pupil centeris detected; and irradiation signal generating means for generating asignal for permitting irradiation of said laser beam in the case thatthe position of the pupil center detected by said pupil center detectingmeans is within the predetermined permissible range of the storedposition of said photographing element.
 5. A corneal surgery apparatusaccording to claim 1, wherein an optical axis of said observationoptical system is coincided with an optical axis of said laser beamirradiating optical system, whereby said observation optical system isalso moved by said first and second moving means.
 6. A corneal surgeryapparatus comprising: an observation optical system for observing ananterior portion of an eye of a patient; and a laser beam irradiatingoptical system for irradiating a laser beam which causes a cornea of theeye ablation, said corneal surgery apparatus ablates the cornea of anarea used for sight of the eye under condition that said irradiatingoptical system is aligned with the eye, the apparatus furthercomprising: illuminating means for illuminating a relatively large areaincluding an iris of the eye; a two-dimensional photographing elementfor photographing a pupil and the iris of the eye illuminated by saidilluminating means; pupil center detecting means for detecting a pupilcenter based on pupil information obtained by processing a signaltransmitted by said photographing element; storage means for storing aposition of the pupil center detected by said pupil center detectingmeans at the time when alignment before surgery is completed; and movingmeans for moving an irradiating position of said laser beam by saidirradiating optical system, by obtaining deviation between the positionof the pupil center detected by said pupil center detecting means andthe position of the pupil center stored by said storage means, so thatthe detected pupil center position may be placed within a predeterminedpermissible range of the stored pupil center position.
 7. A cornealsurgery apparatus according to claim 6, wherein said laser beamirradiating optical system includes a generating light source of anexcimer laser beam, whereby the cornea of the eye is ablated by saidexcimer laser beam generated by said light source.
 8. A corneal surgeryapparatus according to claim 6, further comprising: driving signalgenerating means for generating a signal for driving said moving meansso that the position of the pupil center detected by said pupil centerdetecting means may be placed within the predetermined permissible rangeof the position of the pupil center stored by said storage means, at thetime when the position of the position of the pupil center is detected;and irradiation signal generating means for generating a signal forpermitting irradiation of said laser beam in the case that the positionof the pupil center detected by said pupil center detecting means iswithin the predetermined permissible range of the pupil center stored bysaid storage means.
 9. A corneal surgery apparatus according to claim 6,wherein said pupil center detecting means comprises arithmetic means forcalculating a position of an outer circumference of the pupil based onsaid pupil information and calculating the pupil center based on theposition of the outer circumference of the pupil.
 10. A corneal surgeryapparatus according to claim 1, wherein an optical axis of saidobservation optical system is coincided with an optical axis of saidlaser beam irradiating optical system, whereby said observation opticalsystem is also moved by said moving means.